The present invention relates to a mold for continuous casting of metal, particularly steel, under inclusion of a cooling arrangement, and using a separate uncooled supplemental part which is fastened to the charge end or inlet of the mold.
Molds with particular uncooled charge and inlet structure are know, and they provide for the flow control of the molten metal into the mold without losing any heat, at least not to any significant extent. The supplemental inlet or charge part of course has to be of sufficient thermal insulation, i.e., it must provide in fact a barrier against heat loss from the molten material in order to obtain a pouring flow into the mold at a particular casting temperature so that precipitation, bubbles, cavities, or the like will not be produced.
Another purpose of such a supplemental charge element is the replacement of so-called injection or immersion tubes or pipes. The supplemental charge element is made of ceramic. graphite, or a suitable blend of high temperature resistant material. The utilization of a charge tube or immersion pipe in a mold for continuous casting does permit a reoxidation of the molten material, particularly as far as the metal is concerned as it flows through the pipe. On the other hand, these immersion type casting pipes or tubes are subject to a natural wear which is significant. Moreover, they cause certain precipitation of clay substances in the molten material so that in fact certain remnants so to speak of the casting pipe can be found in the continuous casting and ingot. This of course reduces the quality of the cast metal, which is particularly noticeable and detrimental in case of steel. Therefore, in order to avoid such inclusions, and to ensure a high quality casting texture, one needs several supplemental features in order to make immersion casting pipes and injection tubes for charging a mold feasible; the supplemental features of course have a cost increasing factor as far as the making of the steel product is concerned.
A particular problem concerning durability of casting pipes, charge nozzles, or the like, particularly when they have their ends immersed in the molten steel bath, will occur when casting ingots of fairly thin dimensions, i.e., a casting having a thickness of less than 100 mm. These problems increase with width of the casting.
German printed patent application No. 2,056,532 discloses charging a mold for continuous casting under avoiding of a casting pipe using instead a funnel-shaped additive being coupled to the mold through a fireproof coupler, such that the casting area of the coupler is in fact a continuation of the interior of the mold proper. The opening of the fireproof coupler is provided with an enlargement as an entrance which matches the funnel-shaped feeder supplement. The mold with attachments, coupler, etc., oscillates during casting, but still it was found that this configuration in some form impedes the cooling of the cast material, the formation of a skin, and separation of the casting as it emerges from the mold.
In accordance with another proposal disclosed in German printed patent application No. 1,458,121, corresponding to U.S. patent application Ser. No. 286,349, filed June 7, 1963, in the name of George Robert Gardner, the entrance of the mold for continuous casting is enlarged and an annular insert is tensioned against the front face of the mold. This way one obtains inherently an extension of the insert in radial inner direction, i.e., one obtains a kind of rim above the upper edge of the mold's cavity. The immersion and feeder pipe for this machine ends in the area of that annular insert. This kind of configuration favors indeed flow of the metal from the precooled section established by this annular insert, the flow to occur particularly along the inner wall of the mold proper and the cooling portion thereof. Nevertheless it was found that favorable cooling conditions are not established in such a manner, but they are required particularly for casting of steel. In this sense then this particular suggestion lacks a separation zone for that portion of the casting which has already a somewhat solidified and strengthened skin. Since adequate separation is not ensured, certain inhomogenities in the texture of the casting become more or less unavoidable.